CVE-2026-55603

HIGHPre-NVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.5 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.2%, top 85% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
Elevated
7.5
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 7.5Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

http-proxy-middleware is node.js http-proxy middleware. From 3.0.4 until 3.0.7 and 4.1.1, fixRequestBody() is the library's documented helper for re-emitting a request body that was already consumed by a body parser. When the outgoing Content-Type is multipart/form-data, it rebuilds the body with handlerFormDataBodyData(), which interpolates each req.body key and value directly into the multipart wire format without neutralizing CR/LF. A \r\n inside a value (or key) lets an attacker close the current part and inject an entirely new form part. Because the proxy's own body parser saw a single opaque value, any gateway-side policy or validation performed on req.body is evaluated against a different set of fields than the upstream backend ultimately parses a request/parameter desynchronization across the trust boundary. This vulnerability is fixed in 3.0.7 and 4.1.1.

CVSS v3
7.5
EG Score
7.5(medium)
EPSS
15.4%
KEV
Not listed

Published

June 18, 2026

Last Modified

June 24, 2026

Advisory Details (1)

Auto-updated Jun 22, 2026
🔬 Proof of concept available. Patch available. Sources: github.
github Patch Available🟡 PoC Available

multipart/form-data field injection via unescaped CRLF in `fixRequestBody` · Advisory · chimurai/http-proxy-middleware · GitHub

https://github.com/chimurai/http-proxy-middleware/security/advisories/GHSA-gcq2-9pq2-cxqm

Vendor Advisories for CVE-2026-55603(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(1 across 1 ecosystem)
npm(1)
PackageVulnerable rangeFixed inDependents
http-proxy-middleware—4.1.1—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 23× in last 7d / 57× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-07 02:39 UTCEG score recompute
  2. 2026-07-06 16:27 UTCEPSS rescore
  3. 2026-07-06 16:27 UTCEPSS rescore
  4. 2026-07-06 15:08 UTCEG score recompute
  5. 2026-07-06 03:34 UTCEG score recompute
  6. 2026-07-06 02:23 UTCEPSS rescore
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  8. 2026-07-05 15:41 UTCEG score recompute
  9. 2026-07-05 04:10 UTCEG score recompute
  10. 2026-07-05 02:31 UTCEPSS rescore
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  12. 2026-07-04 16:15 UTCEG score recompute
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  14. 2026-07-03 16:19 UTCEG score recompute
  15. 2026-07-03 04:47 UTCEG score recompute
  16. 2026-07-02 17:16 UTCEG score recompute
  17. 2026-07-02 05:42 UTCEG score recompute
  18. 2026-07-01 18:11 UTCEG score recompute
  19. 2026-07-01 15:07 UTCEPSS rescore
  20. 2026-07-01 06:39 UTCEG score recompute
  21. 2026-06-30 23:22 UTCEPSS rescore
  22. 2026-06-30 19:08 UTCEG score recompute
  23. 2026-06-30 07:38 UTCEG score recompute
  24. 2026-06-29 20:06 UTCEG score recompute
  25. 2026-06-29 14:06 UTCEPSS rescore
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  1. 2026-06-29 14:06 UTCEPSS rescore
  2. 2026-06-29 08:35 UTCEG score recompute
  3. 2026-06-28 21:01 UTCEG score recompute
  4. 2026-06-28 14:07 UTCEPSS rescore
  5. 2026-06-28 09:30 UTCEG score recompute
  6. 2026-06-28 04:56 UTCEPSS rescore
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  8. 2026-06-27 21:59 UTCEG score recompute
  9. 2026-06-27 10:28 UTCEG score recompute
  10. 2026-06-27 03:08 UTCEPSS rescore
  11. 2026-06-26 22:57 UTCEG score recompute
  12. 2026-06-26 11:26 UTCEG score recompute
  13. 2026-06-25 18:53 UTCEG score recompute
  14. 2026-06-25 13:49 UTCEPSS rescore
  15. 2026-06-25 07:22 UTCEG score recompute
  16. 2026-06-24 19:48 UTCEG score recompute
  17. 2026-06-24 14:05 UTCEPSS rescore
  18. 2026-06-24 08:16 UTCEG score recompute
  19. 2026-06-23 21:33 UTCEPSS rescore
  20. 2026-06-23 21:33 UTCEPSS rescore
  21. 2026-06-23 20:45 UTCEG score recompute
  22. 2026-06-23 09:14 UTCEG score recompute
  23. 2026-06-22 21:44 UTCEG score recompute
  24. 2026-06-22 10:08 UTCEG score recompute
  25. 2026-06-21 22:31 UTCEG score recompute
  26. 2026-06-21 10:58 UTCEG score recompute
  27. 2026-06-20 23:25 UTCEG score recompute
  28. 2026-06-20 11:54 UTCEG score recompute
  29. 2026-06-20 00:23 UTCEG score recompute
  30. 2026-06-19 12:50 UTCEG score recompute
  31. 2026-06-19 01:17 UTCEG score recompute
  32. 2026-06-18 13:45 UTCEG score recompute

Frequently asked(5)

What is CVE-2026-55603?
CVE-2026-55603 is a high vulnerability published on June 18, 2026. http-proxy-middleware is node.js http-proxy middleware. From 3.0.4 until 3.0.7 and 4.1.1, fixRequestBody() is the library's documented helper for re-emitting a request body that was already consumed by a body parser. When the outgoing Content-Type is multipart/form-data, it rebuilds the body with…
When was CVE-2026-55603 disclosed?
CVE-2026-55603 was first published in the National Vulnerability Database on June 18, 2026, with the most recent update on June 24, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-55603 actively exploited?
CVE-2026-55603 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 15.4% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-55603?
CVE-2026-55603 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2026-55603?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-55603, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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